Normally you can simply drag the RBrowser into the trash and click "Empty Trash" in the Finder. However, if you had used RBrowser since the last time your host was booted, RBrowser runs a daemon process in the background. This process needs to be killed before you can drag RBrowser into the Trash. Here is how:

Quit RBrowser

Kill the RBDaemon: if you are lazy, just reboot. if not, and you are not afraid of the terminal, issue the following command:/usr/bin/killall RBDaemon

Drag RBrowser to the trash and empty the trash. You are now ready to install a new version!

If you want to totally clear RBrowser off your system, also clear [YOURHOME]/Library/Application Support/RBrowser (the site definitions)
and [YOURHOME]/Library/Preferences/com.objectwarehouse.rbrowser4.plist (global preferences)

To delete up all of RBrowser's files:
Delete the following files/folders:

Site files sit in /Library/Application Support/RBrowser4

Global preferences are in /Library/Preferences/com.objectwarehouse.rbrowser4.plist